Full Magnesium Frame

[Alber]

hi all,
ill be glad to have your thoughts on a full magnesium based frame.
my team have a sposor thats willing to creat an extrusion based magnesium profiles (to our request).
thanx.

[Alber]

hi all,
ill be glad to have your thoughts on a full magnesium based frame.
my team have a sposor thats willing to creat an extrusion based magnesium profiles (to our request).
thanx.

[Jersey Tom]

You mean some sort of spaceframe structure? Welded?

Short answer: I personally wouldn't.

Alloy selection is CRITICAL. I vaguely recall a while ago, flipping through some material properties charts, in Machinery's Handbook I believe, and a lot of the wrought Mag alloys seemed to be fairly mismatched in tensile and compressive strength. You'd have to be sure your sponsor has the appropriate stuff in stock, and that it meets whatever ASTM (or equivalent) certification.

Then there's the whole structural equivalency thing, and the roll hoops..

Mag isn't very stiff.. you'd have to be creative with geometry or just thick sections to make a rigid-enough chassis.

Offhand I want to say aerospace- and ordnance-grade wrought aluminum alloys have much higher strength-to-weight ratios.

Then you'll have to assemble the thing. Cutting members to length and final form, machining tabs and such. You should take extreme care machining mag. It has the potential to be very dangerous, especially if you have water in contact with it (such as flood coolant).

Welding mag... well having a good steel welder is great. Most teams have one. Then there's welding aluminum. You're damn lucky to have someone who can lay down a nice really smooth consistant bead in alum (unless you're doing EBW). I don't know anyone with experience welding mag. When it comes to that kind of thing (machining and welding) it would be very wise to outsource it to someone who really knows what they're doing. And that will probably be expensive.

You can try it though. The chassis is obviously a huge critical path item. I wouldn't do a whole mag frame this year. Stick with what you know. Then over spring and summer, if you really want to check out the feasibility, see if you can get enough material to mock up the front or rear third of your chassis in mag, as well as one in steel. Compare how difficult both are to do, how expensive, stiffness to weight...

When it comes to alternate materials useage I think there are much better choices in terms of benefit and feasibility.

Those are my thoughts, but I'm not a chassis guy.

[Alber]

thanx for replying Tod,
i guess i should give you some more details:

im part of the chassis team and our sponsor is a huge aluminum and Mg profile plant (extrusion, painting, etc.), thay are willing to give all the material needed for free so cost is not a problem for us plus they have the work space, tools and welding expiriance. using a Mg frame will give us a small adventege on other first years and maybe more expirienced teams too, but ide like to know if it was done befor on FSAE and how did it came out?
we did the math and we will cut the weight to HALF even if we use thicker walls.
but the sheer us what im afraid of, do you know anything about that?

[James Waltman]

There was a great article in Road & Track a few years ago about Dan Gurney: "Salon: 1967 All American Racers Eagle-Weslake"�
It also had some really fantastic pictures of present day Gurney driving his 35 year old car.
Find the entire article here. (http://www.roadandtrack.com/article.asp?section_id=33&article_id=368&page_number=1)

From the article - about a magnesium car:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">And if lighter, also much more dangerous. Keep in mind that all GP cars from that era could be deadly, the drivers scorning safety belts because they didn't want to stay with these machines when they crashed. The lightweight Eagle was even scarier, Dan says. "With magnesium you could get a flat tire, have the chassis rub on the ground, catch on fire and you'd never put it out. It's like an incendiary bomb."

Remember that high school chemistry lesson when the teacher lit the little strip of magnesium and demonstrated how it couldn't be doused with water or most of the usual extinguishing methods? How Pierre Levegh's fuel-fired, magnesium-bodied Mercedes-Benz 300SLR continued to burn atop the barriers at Le Mans, 1955?

Did Dan remember all that when he was racing "the magnesium car"? He doesn't pause before answering, "You'd better believe it. That's one reason I didn't have a seatbelt. You hoped to be thrown out," adding chillingly, "It wouldn't help your legs, but at least you wouldn't be singed quite as much." More than ever, crashing became "one of those things you just don't do." </div></BLOCKQUOTE>

[TG]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Jersey Tom:
Mag isn't very stiff.. you'd have to be creative with geometry or just thick sections to make a rigid-enough chassis.

Offhand I want to say aerospace- and ordnance-grade wrought aluminum alloys have much higher strength-to-weight ratios.

Then you'll have to assemble the thing. Cutting members to length and final form, machining tabs and such. You should take extreme care machining mag. It has the potential to be very dangerous, especially if you have water in contact with it (such as flood coolant).

Welding mag... well having a good steel welder is great. Most teams have one. Then there's welding aluminum. You're damn lucky to have someone who can lay down a nice really smooth consistant bead in alum (unless you're doing EBW). I don't know anyone with experience welding mag. When it comes to that kind of thing (machining and welding) it would be very wise to outsource it to someone who really knows what they're doing. And that will probably be expensive. </div></BLOCKQUOTE>

Magnesium isn't stiff? Magnesium actually has a very high specific stiffness. I don't remember the nembers off hand, but definately higher than aluminum. It's specific strength is a little below aluminum.

There have been much improvements in the alloys of magnesium lately that have better physical and corrosive properties. So the Machinists Handbook is a little out of date in that regard. Machining magnesium is as easy as aluminum. Welding is the same as aluminum (welded both last summer).

So, back to the original question. Are the extruded profiles going to be tubes for a space frame or body panels for a monocoque? I would look at it almost like aluminum with slightly different properties. If you were doing a monocoque, there's a thread somewhere on monocoques and an SAE technical paper on them, too. You do have to be careful about corrosion, as magnesium is very suseptable to it. It would be an interesting project, but I'd definately do empirical tests on samples if you aren't planning on heat treatment after any welding.

[Jersey Tom]

Tim...

Elastic Modulus vs Density

Steel | 29mpsi, .29 lbs/ci
Aluminum | 10mpsi, .10 lbs/ci
Magnesium | 6.5mpsi, .065lbs/ci

All pretty damn close. I'm saying its absolute stiffness is very low, so you would have to think through your frame-member geometry carefully.

My Machinery's Handbook is 27th edition, from April 2004. So unless there have been some REALLY recent changes in magnesium metallurgy I can't imagine its that out-of-date.

I'll admit I'm not all that full-up on the 'higher-strength' wrought magnesium alloys, but for light-weight, highly-stressed structural members in aerospace applications it seems stuff like 2090, 7068, and 7475 have all been developed to that end. And I would put money on those having much higher specific strengths than mag equivalents.

With regard to machining..

Its easy if you're talking about its specific horsepower requirements and general free-cutting characteristics. But its dangerous dude. Better be clutch running the right feed and speed at all times, which I almost never see around the student shops here. If for whatever reason it gets hot enough or something makes it ignite, you're in big trouble - for obvious reasons. And if you add water to the burning magnesium mix, it creates a large volume of hydrogen gas very quickly. Boom.

Having talked to some guys who run shops who have cut mag, they all keep a class D fire extinguisher near the machine at all times, and usually a big bucket of sand too, so they can dump it on a flaming part if need be and at least suppress it.

I refuse to cut billet parts from mag here. I'll touch up things if necessary, such as last year on our mag wheel centers I had to open up some bores about 50 thou, ran it 200sfm with plenty of air blast. I just don't feel like worrying about it.

Alber...

Does your weight calculation include the steel main roll hoop and all the bracketry or whatever required to attach it rigidly to the rest of the mag structure?

[murpia]

If your sponsor is offering custom extrusions, you could design something similar to the Lotus Elise bonded aluminium chassis structure. I'm sure a web search will find you a photo of the bare chassis.
[edit] see here: http://www.elises.co.uk/components/s1/chassis/

Integrating the steel roll hoop might prove the hardest challenge.
Ian

[Frank]

wrong dimensional analysis jersey tom

use the formula for a tube in bending.
even though we triangulate to minimise bending in the tube, it is the deflections from moments that dominate the overall chassis torsional stiffness

NOT the thin tube in bending dimensional analysis either (which is the same as member in tension)

you'll need to use factors for sections, and I guess you'll find that the thin wall steel is better

steel, so easy.

[Alber]

thanx all for replying...

Tom...

you are right about Mg burning but your wrong on how...Mg burns when the ratio between surface to mass is huge(i dont have the numbers but we are talking about small chips like those created in a workshop), the alloy we use is AZ80.
about Dan Gorney...yeah it can make your bones chill but we'll attach aluminum sheets beneeth the cockpit and wrep it on the bottom bars(about 2-3 mm).

about the front and main hoop...we intend to attach the hoops with a specific profile and M8 bolts.

ill be glad to get your thoughts on the profile but i dont know how to put it on the forum.

[CMURacing - Prometheus]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by James Waltman:
There was a great article in Road & Track a few years ago about Dan Gurney: "Salon: 1967 All American Racers Eagle-Weslake"�
It also had some really fantastic pictures of present day Gurney driving his 35 year old car.
Find the entire article here. (http://www.roadandtrack.com/article.asp?section_id=33&article_id=368&page_number=1)

From the article - about a magnesium car:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">And if lighter, also much more dangerous. Keep in mind that all GP cars from that era could be deadly, the drivers scorning safety belts because they didn't want to stay with these machines when they crashed. The lightweight Eagle was even scarier, Dan says. "With magnesium you could get a flat tire, have the chassis rub on the ground, catch on fire and you'd never put it out. It's like an incendiary bomb."

Remember that high school chemistry lesson when the teacher lit the little strip of magnesium and demonstrated how it couldn't be doused with water or most of the usual extinguishing methods? How Pierre Levegh's fuel-fired, magnesium-bodied Mercedes-Benz 300SLR continued to burn atop the barriers at Le Mans, 1955?

Did Dan remember all that when he was racing "the magnesium car"? He doesn't pause before answering, "You'd better believe it. That's one reason I didn't have a seatbelt. You hoped to be thrown out," adding chillingly, "It wouldn't help your legs, but at least you wouldn't be singed quite as much." More than ever, crashing became "one of those things you just don't do." </div></BLOCKQUOTE> </div></BLOCKQUOTE>

magnesium is scary shit man. you say they also do aluminum? why not use that? we had ALCOA offer us a similar deal in aluminum a few years ago, but we decided it was too much development for us.

[Jersey Tom]

Gonna stand down on the stiffness bit for a while... though I still feel you will have an easier, stiffer overall design using a thin tube alloy steel design than fat Mag sections.

Up earlier, I wasn't trying to say that you'd have the same stiffness for all 3 options. We had been talking about specific stiffness, and I'm saying Mag isn't anything special in that regard.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">you are right about Mg burning but your wrong on how...Mg burns when the ratio between surface to mass is huge(i dont have the numbers but we are talking about small chips like those created in a workshop) </div></BLOCKQUOTE>

This is exactly what I'm saying. The chips generated during machining have an enormous ratio of surface area to mass. They're going to be less than 10 thousandths thick... more likely on the order of 3-4.

[Denny Trimble]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Jersey Tom:
Gonna stand down on the stiffness bit for a while... though I still feel you will have an easier, stiffer overall design using a thin tube alloy steel design than fat Mag sections.
</div></BLOCKQUOTE>

If you were able to connect the mag extrusions well at the joints, and meet all the safety rules (side impact, rollhoops, etc), the mag frame might be stiffer by a small amount. For the same "weight per foot" of tubing, your mag section will be twice (or more) the OD of your steel section. It will have the same stiffness axially, but its bending stiffness will be much greater than the steel tube of the same mass. Spaceframes ideally feed only axial loads into the members, but some bending still exists.

Packaging will be more difficult, joining will be more difficult, and you will end up having at least a steel main roll hoop, so the total weight savings and stiffness increase (especially if your joints are heavier and less stiff than welded steel tubing joints - which they probably will be) are very small, maybe even negative.

[fsae_alum]

Speaking from experience, doing this for a first year car is probable suicide (in terms of your ability to compete). For our first year car, we decided to do an aluminum frame and we basically got our arses handed to us by the judges for doing so. Remember, Keep It Simple.

How are you planning on attaching the extrusions together? Welding, bonding, bolting?
If you're welding, you will probably have to use the "as-welded" strength for all your calcs and it can be tricky to get those numbers and get the judges to buy off on them.
If you're bonding prepare for intense scrutiny about bond prep and quality. Have testing to back it up. What about joint fatigue?
If you're bolting, how does that work out for weight.

Listen, from first hand experience, your team will have a hard enough time for your first year without having to deal with the unknowns and problems associated with dealing with competition non-standard materials. Stick with steel, it will make your life much easier. Hell, due to the safety concerns, they may not even let you run a mag frame. Sure would suck to waste all that time designing it and then find out that you can't use it.

[jack]

a frame made of cheese?! sounds interesting....

refer to sig

[Alber]

fsae_alum...
is their a way to know for sure if they'll allow the frame, couse in the end we will meet the requierments.

were gonna use welding and the factory has 30 years expiriance with Mg welding.

indeed all our time is being spent on profile selection.

and you'r right about sheer its pretty lousy in Mg but with proper profiles and flanges we can make it stiff and still we will save alot of wheight.

[Jersey Tom]

Well in any case, best of luck with it, Alber.

[Cement Legs]

[QUOTE]Originally posted by fsae_alum:
Speaking from experience, doing this for a first year car is probable suicide (in terms of your ability to compete). For our first year car, we decided to do an aluminum frame and we basically got our arses handed to us by the judges for doing so. Remember, Keep It Simple.

How are you planning on attaching the extrusions together? Welding, bonding, bolting?
If you're welding, you will probably have to use the "as-welded" strength for all your calcs and it can be tricky to get those numbers and get the judges to buy off on them.

QUOTE]

Did you guys heat treat your aluminum frame? What were the judges biggest complaints other than saying that aluminum doesnt belong on a race car space frame (pretty big argument, i know)? I'm asking because we have a full rolling chasis right now and its made out of aluminum. I suppose it would be easy enough to weld up a steel frame to the same dimensions with smaller tubing but we would preffer to just run with what we have. Any suggestions would be very much welcomed. Also I've looked for information on the "as welded condition" and havent had any luck digging anything up.

[fsae_alum]

Alber:
You'll need to ask Steve Daum and Kathleen McDonald if they will allow you to use the frame. You can do what you what, and of course I wish you the best of luck, but I have to tell you from experience that your team is taking the long and hard road to your ultimate destination. For your first time out of the gate, you are biting off a mighty big chunk of work. You will have to run your equivalency calculations based on either the as-welded state or the heat treated state (based on if you heat treat or not).

Cement Legs:
We designed our frame around the heat treated strength. We talked to a very reputable heat treater long before we agreed to go down the path of an aluminum frame and they said that it would be no problem to heat treat the frame. We commenced building the frame and it fit together beautifully. We had a certified aircraft welder come over and weld it for us and it looked great. Drove 2 hours to drop it off at the heat treater. Next day we got a call from the heat treater that said "Yeeeeeahhhhh.....ummmm....we CAN heat treat your frame, but when we do, we guarantee that it will end up looking like a big pretzel and will be nothing like what you are hoping for." Ok, now we had to see if we met equivalency in the as-welded state. Luckily enough for us, we barely did. There is a particular book that Kathleen McDonald said that we had to pull all of our numbers from to use for the as-welded state calculations. Even after all that, when we got to competition, the judges pretty much told us that as you said, Aluminum has no business being used for racecar frames. We pointed out how we designed the frame to be precise and very easy to mass produce and easy to assemble but none of that mattered. They grilled and hammered us about fatigue strength to which we replied "It's only used for one race....this one." but they still hammered us on it. Later on in our trailer, a judge from Ricardo told us that our single biggest mistake was going with an aluminum frame and that basically the only reason the judges let us compete was because they somewhat felt sorry for us. So there you go. Best of luck and may your journey be smoother than ours was.

[Alber]

wow...
you realy pulled the the air from my sail...damn.

but the wheels are allready set in motion and itll be harder to stop them now, well ill be glad to get as many helpfull tips in spite of...

1)do you know any good matirial to put underneeth the chassis to prevent tuching the ground in case of suspension feiliure?

2)what profile dimantions did you use for other spots in the car (except side, hoops, etc.)? the steel i mean ill do the math for Mg.

3)do you know of any good experiment that the juges will be pleased of for fatigue?

look everyone your right to be scared shitless of Mg and probably i should do too, but i belive in inovation and making things work when they shouldnt i want this project to work its my challange and their wont be a happy man than me if youll help me make it.

again thanx all.

[Draksia]

The only thing that scares me more then Mg is Beryllium.


Which is really too bad because it makes a great engineering material.

[fsae_alum]

Wasn't trying to pull the air from your sail, just trying to let you know that the path of innovation can be a painful and time consuming path. I do however wish you the best of luck in your endeavor.

To answer your questions:
1.) You can use Aluminum sheet or even wood rails.

2.) For tubing we used 1.5 x 1.5 square tubing with a 0.100 wall. The tubing was notched so that it locked together at the joints and was then welded together. We machined bulkheads out of billet and spaced the bulkheads using machined spacers and the tubes locked into places on the bulkheads and were welded in place.

3.) Good experiments for fatigue? Don't know any. We had a good deal of data for Aluminum that we pulled from a source close to Boeing that provided fatigue and material properties in the as-welded condition. Being that Magnesium is not heavily used in load bearing structures all that much, I wouldn't even know where to point you to get the data you are looking for. What I was trying to imply and say was that if you look at how many times a FSAE car is run, frame weld fatigue should not be an issue. The judges however used it as a reason to not use Aluminum....even though it didn't really apply due to the life cycle of the frame.

If you are bnding, then the fatigue is taken up by your bond strength and there IS data on that from Loctite (Hysol).

Hope that helps some.

Thanks!

[yofa]

ask your sponsor if he'd drive the car. that might change his mind.

seriously, in the interest of safety, i'd be really reluctant to try an aluminium frame because of the joining issues, and wouldn't dare look at a mag frame.

the c6 z06 road car has an alum frame. the c6.r race car uses the steel version. with the extra downforce and grip, and the fact that all cars have to meet minimum weight anyway, trying to use the alum bits probably didn't make sense.

as a new team, there's a lot that can be learned by just building an average car and showing up to competition. if you manage to get something reliable here and finish all the dynamic events, you may surprise yourself by beating most teams.

[Storbeck]

I believe there are a few magnesium parts on the new z06 as well.

Are you guys talking about a magnesium space frame, or a magnesium tub? Seems like a magnesium space frame, like an aluminum space frame, just doesn't seem like such a great idea, I don't see the advantages. Panels cut and folded, riveted and bonded, might make a nice light chassis. Could end up being less work for the mag than a steel space frame, if done right.

[Cement Legs]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by fsae_alum:

Cement Legs:
Later on in our trailer, a judge from Ricardo told us that our single biggest mistake was going with an aluminum frame and that basically the only reason the judges let us compete was because they somewhat felt sorry for us. So there you go. Best of luck and may your journey be smoother than ours was. </div></BLOCKQUOTE>

hmmmmm 4130 steel.... hmmmmmm

For what parts do you need the structural equivalency? Is it just the frame? i.e. if your a arms are CF do you need the equivalency form for those as well?

[fsae_alum]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Cement Legs:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by fsae_alum:

Cement Legs:
Later on in our trailer, a judge from Ricardo told us that our single biggest mistake was going with an aluminum frame and that basically the only reason the judges let us compete was because they somewhat felt sorry for us. So there you go. Best of luck and may your journey be smoother than ours was. </div></BLOCKQUOTE>

hmmmmm 4130 steel.... hmmmmmm

For what parts do you need the structural equivalency? Is it just the frame? i.e. if your a arms are CF do you need the equivalency form for those as well? </div></BLOCKQUOTE>

I know, I know ....we proved equivalency, but if they don't like it.....they don't like it, and there is no rule that says that if you make your car out of clay and it passes equivalency then it is a great idea to use that frame material.
Furthermore, just because you pass equivalency, that doesn't mean that the judges will LIKE your choice of materials. Meeting the rules and making the judges happy are two different things. Know what I'm saying here?
Just because you can....doesn't mean you should.

[Cement Legs]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by fsae_alum:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Cement Legs:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by fsae_alum:

Cement Legs:
Later on in our trailer, a judge from Ricardo told us that our single biggest mistake was going with an aluminum frame and that basically the only reason the judges let us compete was because they somewhat felt sorry for us. So there you go. Best of luck and may your journey be smoother than ours was. </div></BLOCKQUOTE>

hmmmmm 4130 steel.... hmmmmmm

For what parts do you need the structural equivalency? Is it just the frame? i.e. if your a arms are CF do you need the equivalency form for those as well? </div></BLOCKQUOTE>

I know, I know ....we proved equivalency, but if they don't like it.....they don't like it, and there is no rule that says that if you make your car out of clay and it passes equivalency then it is a great idea to use that frame material.
Furthermore, just because you pass equivalency, that doesn't mean that the judges will LIKE your choice of materials. Meeting the rules and making the judges happy are two different things. Know what I'm saying here?
Just because you can....doesn't mean you should. </div></BLOCKQUOTE>

Actually I was agreeing with you... note the switch to 4130... but I guess my question is do you have to do structural equivalency for a-arms or just frame built with alternative materials?

[Schulberg J]

Original Porche 917 frames were aluminum, and they had big problems with fatigue cracking. Steel sure is nice when it comes to fatigue...

[Travis Garrison]

Why are you discussing welding al or mg at all? That really doesn't make much sense. I would agree with the judges, a welded aluminum frame has no place in racecar, but a bonded al or mg frame, now your talking. Take a look at how the lotus elise is put together, there is a great example of how to do it right. If you can get a few extrusions made to your specs it will make the corner work MUCH easier. Mg extrusions, al sheet...

As for the SSEF, it's not a big deal. You'll need to do it, but its mostly just checking E x I steel = E x I your material...nothing to be afraid of.

I'd say go for it. A bonded tub won't be any more difficult than a spaceframe, and it's a lot closer to a production ready design than an intricate spaceframe.

[fsae_alum]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Travis Garrison:
Why are you discussing welding al or mg at all? That really doesn't make much sense. I would agree with the judges, a welded aluminum frame has no place in racecar, but a bonded al or mg frame, now your talking. Take a look at how the lotus elise is put together, there is a great example of how to do it right. If you can get a few extrusions made to your specs it will make the corner work MUCH easier. Mg extrusions, al sheet... </div></BLOCKQUOTE>

The original poster was talking about making a spaceframe out of Mg. That usually implies welding. All I was trying to do was point out the pitfalls of that. We learned our lesson the hard way and I was just trying to ensure that the original poster does not have to go down that same painful path.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
As for the SSEF, it's not a big deal. You'll need to do it, but its mostly just checking E x I steel = E x I your material...nothing to be afraid of.
</div></BLOCKQUOTE>
I agree....it's not that hard to prove equivalency but my earlier point was that proving equivalency does not necessarily mean that the judges will like your design.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
I'd say go for it. A bonded tub won't be any more difficult than a spaceframe, and it's a lot closer to a production ready design than an intricate spaceframe. </div></BLOCKQUOTE> Ahhhh...but will the judges allow it due to safety concerns?

[Travis Garrison]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by fsae_alum:


The original poster was talking about making a spaceframe out of Mg. That usually implies welding. All I was trying to do was point out the pitfalls of that. We learned our lesson the hard way and I was just trying to ensure that the original poster does not have to go down that same painful path.
</div></BLOCKQUOTE>

Sorry, I didn't phrase that well. I meant why would they be considering it in the first place, I have 0 experience with welded magnesium but from what I gather it's similiar to al, and that's just a disaster waiting to happen. You'll need a GOOD welder, CLEAN material and even then there's a good chance it will crack somewhere down the road...why would you do that to yourself?

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
I agree....it's not that hard to prove equivalency but my earlier point was that proving equivalency does not necessarily mean that the judges will like your design.
</div></BLOCKQUOTE>

Sure if you're talking about a welded al or magnesium frame. And there's a damn good reason they didn't like the aluminum frame, esp when welded by students...it's probably going to crack at some point...


<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
Ahhhh...but will the judges allow it due to safety concerns? </div></BLOCKQUOTE>

I'm suggesting an al monocoque with magnesium extrusions shaped to help joining the corners, in which case I would be very supprised if they didn't love it. There have been aluminum moncocques for years in FSAE and about a decade or more in F1 & indy (70's - early 80's for F1, longer for indy I believe), so there's no question about safety there. If we're talking about a bonded frame, WWU's been doing it for years and there has never been a complaint about it, so again I can't imagine any problems there.

My point is it sounds like they have a great opportunity on their hands, extrusions made to order, out of magnesium no less, make a metal monocoque very realistic. I'd say go for it...just stay well away from the welder.

[Igor]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
...why would you do that to yourself?
</div></BLOCKQUOTE>

You can polish it to a shine http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

Note that Delft won design in the UK in 2003 with a carbon tub/rear aluminium spaceframe, so not all judges are opposed to the use of aluminium. Must have been the polishing http://fsae.com/groupee_common/emoticons/icon_smile.gif

Edit: Back then it was allowed to have an aluminium roll bar, so it made more sense then than now.

Igor

[Travis Garrison]

good point...I forgot about delft...I personaly would still avoid welded aluminum, but obviously it can be done well...

[Andycostin]

I'm not going to get into this in depth, I think Colin or Rene would be able to talk about it more, but last year and again this year we've used cast Magnesium sections in our stressed rear end, and also our uprights and pedal box, I can't see why this sort of material use isn't appropriate for other areas too, just depends how much time you've got to develop it all http://fsae.com/groupee_common/emoticons/icon_smile.gifhttp://www.swin.edu.au/feis/fbr/images/photos/testing/2005Testing2-03.jpg

[Omer]

hi all
i'm from the full mag frame team down in Israel,we still have a way to go but we build our frame and starting to assemble the car.
you can see it here,go to Gallery.
http://w3.bgu.ac.il/sae-car/index.html

[Jersey Tom]

Those uprights cast?

[Blake_DFSAE]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Storbeck:
I believe there are a few magnesium parts on the new z06 as well.
</div></BLOCKQUOTE>

Engine cradle's a mag piece. Big bastard too.

[Omer]

Uprights are cnc from mag.

[D-Train]

Last year at the design event, the judges weren't terribly convinced that there was no danger of fire with our magnesium uprights, since we ran outboard brakes. They wanted temprerature logs of them to prove it, and I guess they'd probably drill you guys a fair bit more with a magnesium chassis, so keep that in mind around any areas of the chassis that lie near sources of heat.

[billywight]

Have you ever tried to light a chunk of Mg on fire? (I mean a chunk, not shavings) Good luck with that. I'm really suprised the judges were worried about the uprights catching fire from the brake heat. Many older open wheel cars had Mg uprights without problems.

[Blake_DFSAE]

Agreed - you need to melt the piece for it to catch. Judges worrying about that is a little much.

Now for pieces scraping off, that's a viable issue, but unless there's danger of that happening it's all good.

[drivetrainUW-Platt]

first, I thought you were working with a "professional shop"
http://w3.bgu.ac.il/sae-car/174-7438_IMG.jpg not professional
according to your cad files/parts, it looks like you are using aerodynamic a arm tubing, that has been discussed on this forum and determined to be pointless and unsafe in our competitions
personally I think a 1" dia round tube frame looks way cooler then a 1.5" square......no matter what the material

[Jersey Tom]

I wouldn't go so far to call any tubes not CNC mandrel bent to be 'unprofessional'. Nothing wrong with simple dies.

Aero tube isn't unsafe, unless its too thin to be supporting the loads transferered through it. Being worthwhile or not is a different story.

And I agree on the mag uprights. No inherent danger there unless there's the possibility of a brake rotor or bobbins or what have you coming loose and simultaneously shaving off bits of mag and transferring lots of heat there.

Formula Atlantic even ran Mag uprights until very recently.

[TG]

My dad told me of a porsche magnesium engine block catching fire. He said it was the first 911 SC in Wisconsin. The guy lost control of the car on a bridge (I don't remember if he said there was ice) and took a dive off. After the impact the block somehow managed to catch fire and people could see it from miles around.

But as long as we don't drive at the Catapillar proving grounds, I'd say we're safe from cliff dives and catching large pieces of magnesium on fire.

[KU_Racing]

anyone else think heat bending mag is a bad idea?
doesnt magnesium have not-too-great fatigue properties?? A friend of mine had mag center kaisers on his street car.. they cracked pretty bad, the canters fatigue cracked completely out on 3 of them.

[Jersey Tom]

Heat bending it.. depends how much heat you put in. I dont have much experience metalworking Mag though. Think it starts recrystalizing as low as 600F.

Fatigue resistance.. don't know. I've never heard of it being great. Same with fracture toughness. Just doesn't seem like it would be all that great.

A lot of the datasheets floating around for mag alloys (AZ31B.. AZ80A..) are for forgings, not machined parts, and as such anything machined is gonna be substantially weaker. On any mag part I'd definately radius the hell out of it, polish it if possible, and glass bead peen it, just to get its toughness up a bit. That and/or some sort of hard surface coating.

[Matt Gignac]

From the looks of things though, those hoops are steel and sit in some Mag channels on the frame, probably bolted or bonded or something. Besides, the rules say the hoops have to be round steel tube.

Matt Gignac
McGill Racing Team

[Bill Kunst]

...or structurally equivelant. Make sure that you read the rules closely. I have seen full aluminum frame cars at comp, all they had to do was file a form in advance showing equivelant strength.
Bill

[Matt Gignac]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">3.3.4.2 Main Hoop
(A) The Main Hoop must be constructed of a single piece of uncut,
continuous, closed section steel tubing per Section 3.3.3.
(B) The use of aluminum alloys, titanium alloys or composite materials
for the Main Hoop is prohibited. </div></BLOCKQUOTE>

and

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
3.3.3.2.1 General
...
The main roll hoop and main roll hoop bracing must be made from steel,
i.e. the use of aluminum or titanium tubing or composites are prohibited
for these components. </div></BLOCKQUOTE>

By 3.3.4.2 you'd think you can use magnesium for the hoop (only says Al, Ti or composites), but then there's 3.3.3.2.1. However, I just realized now you can use equivalent materials for the front hoop, so maybe that was the case in the pictures from Ben Gurion.

There were aluminum frames back in the day, but I think the closest recently was UQAC, with everything aluminum except the main hoop and main hoop bracing... one of the perks of being on Alcan's doorstep. Maybe Delft a few years back too the first year they went to being crazy and little.

Matt Gignac
McGill Racing Team